Rename minRepetitions to maxRepetitions and clamp with min()

The value minRepetitions is actually used as an upper bound. Looks like
this was a misunderstanding of a review comment in
https://codereview.chromium.org/251643002.

BUG=404023

Review URL: https://codereview.chromium.org/479493002

git-svn-id: svn://svn.chromium.org/blink/trunk@180331 bbb929c8-8fbe-4397-9dbb-9b2b20218538